Liquid manure from animal husbandry operations, particularly pig farming operations, is typically stored in a large manure reservoir or lagoon until there is a sufficient quantity available to spread or irrigate onto farm land for disposal. In order to remove the manure from the reservoir, a pump is used that is typically located alongside the reservoir and lowered into the reservoir. The pump can be free standing or attached to a tractor, which is often preferable to provide stability to the pump and a source of motive power for the pump.
The volumetric flow rate of fluid handled by the pump is large, typically in excess of 4000 gal/min; accordingly, it is desirable that the pump be efficient in terms of providing the required flow with minimal energy loss. Efficient pumps permit use of smaller tractors for providing motive power and reduce the fuel consumption of the tractor, reducing pump operating cost. In addition, it is desirable that the pump have large fluid openings and generous tolerances in order that solid material in the reservoir can be accommodated by the pump without plugging; this works against pump efficiency and makes it extra important to capitalize on efficiency gains wherever else they might be available.
Since the surface of the reservoir is variable in height relative to the side, due to either variation in the degree to which the reservoir is filled or due to removal of manure from the reservoir by pumping, it is desirable to have a pump with a variable depth position and optionally orientation relative to the surface. This is commonly accomplished by lowering the entire pump towards the surface, which often requires the tractor to be positioned dangerously close to the edge of the reservoir and is not suitable for all situations, particularly lagoons with gradually sloped sides or reservoirs with elevated sides.
In addition, it is desirable to have some means of surface agitation, either separate from the pump or incorporated into the pump itself, to disrupt formation of a cake or blanket on the surface of the reservoir and/or to prevent foam formation during pumping. The means of agitation often comprises a nozzle for re-directing a portion of the pumped fluid back to the surface of the reservoir; however, these nozzles are typically fixed and lack the ability to be positioned to break up cakes and foam.
Accordingly, there still exists a need for improved pumps, particularly pumps that are positionable alongside a fluid reservoir for immersion within the reservoir.